Abstract: Vertical gender segregation is one of the most stubborn features of labor markets: high-ranking positions are primarily held by men in Business, Politics and Science. Can we design an institution, an affirmative action, to erase this segregation? We try to answer this question by investigating the effects of a clear affirmative action for women, where we have a good measure of “ability” even of people who did not directly benefit from the action. Chess, which is grappling with a huge vertical segregation problem, offers a special and unique opportunity to investigate the effect of an affirmative action, because we have a clear idea how good someone is. France introduced an affirmative action (AA) for women in its club competitions in the beginning of the nineties, which helps us to answer key questions. How much does the AA benefit the selected pool? Does the AA trickle-down? In other words, does it lead to higher investment (benefits) of a whole group and not just those selected?